Wireless communication method, wireless transmitter and wireless receiver

ABSTRACT

A wireless communication method by which unnecessary retransmission request is suppressed and feedback information is reduced at the same time in a MIMO communication system. The wireless communication method is provided for transmitting signals by using a plurality of antennas, and has a step of applicably selecting the group configuration of the antennas, and a step of adding data to be used for error detection to a signal to be transmitted by using the antennas, by following the results of the selection.

BACKGROUND

1. Technical Field

The present invention relates to a wireless communication system,wireless transmitting apparatus and wireless receiving apparatus used ina MIMO (Multiple Input Multiple Output) communication system.

2. Description of the Related Art

Simultaneous transmission of multiple data streams is carried out in aMIMO communication system that employs multiple (N_(T)) transmittingantennas and multiple (N_(R)) receiving antennas. Signals travel fromthe transmitting antennas via a plurality of paths, undergoingreflection and scattering before arriving at the receiving antennas. Akey feature of MIMO systems is the ability to exploit multipathpropagation, turning it into a benefit for the user. One such advantageis the increase of system capacity through the use of spatialmultiplexing, typically achieved by transmitting independent data onindividual transmit links.

With future technology shifting to accommodate a high speed, moreIP-based data service, requirements such as spectral efficiency, systemuser capacity, end-to-end latency, and quality of service management,need to be satisfied. One of the techniques that play a crucial part inmeeting some of these criteria is automatic repeat request (ARQ). ARQ isuseful for ensuring fast and reliable delivery.

ARQ is a technique for sending a retransmission request for receivedpacket data upon detection of an error in the received packet data. Withthe transfer of a large amount of high-speed data, more efficient ARQtechniques are typically used to reduce the number of retransmissionrequests.

In a typical implementation of ARQ, each packet is associated with CRC(Cyclic Redundancy Check) for the purpose of error detection. At thereceiver, the content of each packet is validated through the use ofCRC. If the packet content is found to contain errors, the receiver willrequest a retransmission. In the case of MIMO systems, single CRC data(hereinafter “single CRC”) is simply attached to a packet and thispacket is sent using multiple antennas. Since substreams transmittedfrom different antennas normally experience different link conditions,these antennas have different error statistics. The probability thatsignals on all antennas have errors is very small, especially when alarge number of antennas are employed. Since only single CRC is used,the whole packet has to be retransmitted if errors are detected.Therefore, substreams that have already been correctly received areretransmitted, and throughput is wasted beyond necessity.

A method of reducing unnecessary retransmission is proposed inNon-Patent Document 1. The method proposed makes use of encoders perantenna which make ARQ processes performed in each substream. Usingmultiple encoders per antenna, it is possible to eliminate theconstraint of sharing single ARQ processing by multiple transmittingantennas, and multiple acknowledgement signals are sent back to thetransmitter which decides whether to retransmit the substreams in error.Hence, throughput can be increased significantly, and error-freesubstreams need not to be retransmitted.

Non Patent Document 1: “Multiple ARQ Processes for MIMO systems”, theIEEE International Symposium on Personal, Indoor and Mobile RadioCommunications 2002.

BRIEF SUMMARY Problems to be Solved by the Invention

Although using only single CRC for multiple antennas causes unneededretransmission when received signals from only one or two antennas arefound to contain errors, the employment of multiple ARQ processes usingmultiple CRC data {hereinafter “mufti-CRC”) can solve this problem.However, ARQ processes using multi-CRC causes an increase of uplinksignaling overheads due to multiple acknowledgements (that is, feedbackinformation) and this needs to be considered, especially when the numberof antennas to be used is large. That is, in the ARQ system of relatedart, it is difficult to control unneeded retransmission and reducefeedback information.

it is therefore an object of the present invention to provide a wirelesscommunication system, wireless transmitting apparatus and radioreceiving apparatus that can control unnecessary retransmission in aMIMO system and reduce feedback information.

Means for Solving the Problem

The wireless communication method of the present invention fortransmitting a signal using multiple antennas employs a configurationhaving: a selecting step of adaptively selecting a group configurationof the multiple antennas; and an attaching step of attaching data usedin error detection to a signal to be transmitted using the multipleantennas according to a result of selection.

The wireless transmitting apparatus of the present invention employs aconfiguration having: multiple antennas; a selecting section thatadaptively performs selection of the multiple antennas; an attachingsection that attaches data used in error detection to a signal to betransmitted using the multiple antennas according to a result ofselection by the selection section; and a transmitting section thattransmits the signal with the data attached by the attachment section.

The wireless receiving apparatus of the present invention having:multiple antennas; a receiving section that receives through themultiple antennas a signal to which data used in error detection isattached according to the result of selection of the group configurationof the multiple antennas; and a detecting section that performs errordetection on the signal received by the receiving section using the dataattached to the signal.

Advantageous Effect of the Invention

According to the present invention, it is possible to controlunnecessary retransmission and reduce feedback information in a MIMOsystem.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates an example of a configuration of a transmitter inwhich single CRC is attached;

FIG. 1B illustrates an example of a configuration of a receiver in whicherror detection is performed by single CRC;

FIG. 2A illustrates an example of a configuration of a transmitter inwhich multi-CRC is attached;

FIG. 2B illustrates an example of a configuration of a receiver in whicherror detection is performed by multi-CRC;

FIG. 3A illustrates a configuration of a transmitter according to anembodiment of the present invention;

FIG. 3B illustrates a configuration of a receiver of an embodimentaccording to the present invention;

FIG. 4A illustrates an antenna configuration of an embodiment accordingto the present invention;

FIG. 4B illustrates another antenna configuration according to anembodiment of the present invention;

FIG. 4C illustrates another antenna configuration according to anembodiment of the present invention;

FIG. 5 illustrates a first example of antenna configuration selectionupon retransmission according to an embodiment of the present invention;

FIG. 6 illustrates a second example of antenna configuration selectionupon retransmission according to an embodiment of the present invention;

FIG. 7 illustrates a third example of antenna configuration selectionupon retransmission according to an embodiment of the present invention;and

FIG. 8 illustrates a fourth example of antenna configuration selectionupon retransmission according to an embodiment of the present invention.

DETAILED DESCRIPTION

An embodiment of the present invention will be described in detail belowwith reference to the accompanying drawings.

FIGS. 1A and 1B are diagrams of a MIMO wireless communication system inwhich single CRC is attached. FIG. 1A illustrates the configuration of atransmitter, and FIG. 1B illustrates the configuration of a receiver.

Referring to FIG. 1A, at the transmitter, data processing is performedfor a single stream of information, regardless of the number of antennaspresent. First, CRC attachment 102 is performed on inputted binary data,and channel coding 104 (such as convolutional coding and turbo coding)is carried out on the binary data. The encoded data will then bemultiplexed into a plurality of streams to be transmitted through thevarious antennas, and interleaving 106 is performed on streams onrespective antennas so as to reduce burst errors in the data. Symbolmapping 108 is carried out on the interleaved data using multipleamplitudes and multiple constellations. Pilot signal insertion 110 willbe performed for performing channel estimation at the receiver.

Prior to transmission, the digital signal is converted to analog signalby digital to analog converter (DAC) module 112. After the aboveprocessing, signals will be ready for transmission through theirallocated transmitting antenna 114.

Referring to FIG. 1B, at the receiver, the reverse processing to theabove-described processing, like analog to digital conversion by analogto digital conversion (ADC) 118, is performed on the signal received atreceiving antennas 116. Since a received signal includes overlappingsignals from multiple transmitting antennas 114, it is necessary toseparate the received signal into individual streams. This separatingprocessing is performed through the use of MIMO demodulating 120, suchas inverse channel matrix, maximum likelihood detection or V-BLASTtechnique.

Further, after demapping 122 and deinterleaving 124, the data will bedemultiplexed into the original packet size, and decoding 126 will beperformed on the packet. Finally, CRC error detection 128 is carried onthe packet to validate the data. If the packet checked is decided to beerror free, an ACK (acknowledgement) is sent to the transmitter, and thetransmitter will not retransmit the packet. By contrast, a NACK(negative acknowledgment) is sent to the transmitter in order to requestretransmission.

FIGS. 2A and 2B illustrate a MIMO wireless communication system withinwhich multi-CRC technique is applied. FIG. 2A shows the configuration ofa transmitter, and FIG. 2B shows the configuration of FIG. 2B.

Referring to FIG. 2A, interleaving 206, symbol mapping 208, pilot signalinsertion 210, DAC 212 and transmitting antenna 214 in this transmitterare the same as interleaving 106, symbol mapping 108, pilot signalinsertion 110, DAC 112 and transmitting antenna 114 shown in FIG. 1A,respectively. The transmitter of FIG. 2A differs from that of FIG. 1A inthat the transmitter of FIG. 2A includes multiple CRC attachment 202grid multiple channel encoding 204.

This means that every data packet on each individual receive antennachain will undergo CRC error detection for error detection. Receivingantennas 216, ADC 218, MIMO demodulating 220, demapping 222 anddeinterleaving 224 in this receiver is the same as receiving antenna116, ADC 118, MIMO demodulating 120, demapping 122 and deinterleaving124 shown in FIG. 1B, respectively. The receiver of FIG. 2B differs fromthat of FIG. 1B in that the receiver of FIG. 2 has multiple decoding 226and multiple CRC error detection 228.

The receiver will then feedback ARQ information for each of the datastreams via a fast ARQ feedback channel to the transmitter. Advantagesof this configuration include that it eliminates the need to retransmitthe data from all antennas whenever an error is detected. Only thosedata streams that are corrupted require retransmission. The probabilitythat all data streams have errors is low, so that this transmissionmethod can improve the data throughput.

FIGS. 3A and 3B illustrate MIMO wireless communication system accordingto an embodiment of the present invention. FIG. 3A illustrates theconfiguration of a transmitter, and FIG. 3B illustrates theconfiguration of a receiver. Further, in this case, although atransmitter and a receiver each having four antennas will be describedfor ease of explanation, the number of antennas of the transmitter andthe number of antennas of the receiver according to the presentinvention are not limited to four. A transmitter and receiver applied tothe present invention may have multiple antennas forming MIMO channel.

The transmitter of FIG. 3A has transmitting antenna configurationselection 301, CRC attachment 302, channel encoding 304, interleaving306, symbol mapping 308, pilot signal insertion 310, DAC 312 andtransmitting antenna 314. Channel encoding 304, interleaving 306, symbolmapping 308, pilot signal insertion 310, DAC 312 and transmittingantenna 314, which configure a transmitting section that performs signaltransmission, are the same as channel encoding 204, interleaving 206,symbol mapping 208, pilot signal insertion 210, DAC 212 and transmittingantenna 214 of the above-described transmitter, respectively. Althoughthe operation of CRC attachment 302 is basically the same as CRCattachment 202, the operation is controlled by transmitting antennaconfiguration selection 301. The transmitting antenna configurationselection 301 will be described later.

The receiver of FIG. 3B has receiving antenna 316, ADC 318, MIMOdemodulating 320, demapping 322, interleaving 324, decoding 326,receiving antenna configuration selection 327 and CRC error detection328. Receiving antenna 316, ADC 318, MIMO demodulating 320, demapping322, deinterleaving 324 and decoding 326, which configure a receivingsection that performs signal reception, are the same as receivingantenna 216, ADC 218, MIMO demodulating 220, demapping 222,deinterleaving 224 and decoding 226 of the above-described receiver,respectively. Although the operation of CRC error detection 324 isbasically the same as CRC error detection 228, the operation iscontrolled by receiving antenna configuration selection 327. Receivingantenna configuration selection 327 will be described later.

Transmitting antenna configuration selection 301 will be describedbelow.

FIGS. 4A, 4B and 4C illustrate an example of antenna configurationsprovided by the present invention, that is, an example of antennaconfigurations selected by transmitting antenna configuration selection301.

FIG. 4A shows the type I configuration, which is the system that hasbeen described using FIGS. 1A and 1B. In this configuration, single CRCis attached to the data packet regardless of the number of antennaspresent. The advantage of employing this type of configuration is thatthe size of the packet undergoing channel coding will become larger. Alonger code usually can help reduce an error rate as compared to ashorter code.

FIG. 4B shows the type II configuration, which is the system that hasbeen described using FIGS. 2A and 2B. In this configuration, CRC data isattached on each packet on different antenna chain. By doing so, itensures fast response for ARQ as only antenna streams where error occursneed to be retransmitted. In this way, the overall throughput canincrease significantly.

FIG. 4C shows the type III configuration. This configuration is acombination of type I and II configurations. This type aims to achieve abalance to obtain a low error rate and reduce the latency. Otheradvantages include reducing the signaling overheads required formulti-CRC and controlling the reduction of unnecessary retransmissiontogether.

Several criteria can be applied when a configuration is selected fromthe three antenna configurations. One is to select the transmission typeaccording to quality of service (QoS) requirement. Other criteriainclude selection based on ARQ feedback information, channel feedbackinformation or the employed modulation and coding scheme (MCS).

The first preferred embodiment of the present invention describesantenna configuration selection according to QoS requirements. Formeeting the end-user QoS requirements for various applications, a systemwould need to support the configuration of a flexible set of trafficclasses with different latency and packet error rate performance.

The present invention can support different sets of traffic classes,which mainly encompass two main types of requirements related to QoS.The system has to meet either low error rates or low latencyrequirement. For systems that require low latency, transmission of alarge amount of data is frequently required in a short time whileaccuracy takes second place. Some examples of such applications includevideo streaming and fax.

On the other hand, for systems requiring lower error rates than acertain rate, the accuracy of data is the most important factor. Theseapplications include e-commerce, web browsing, email access and otherinteractive services such as instant messaging.

Therefore, when antenna configuration selection is performed accordingto QoS requirements, it will be suitable to assign type I configurationfor systems requiring low error rates and type II configuration tosystems requiring low latency. Since error-intolerant but delay-tolerantsystems do not request fast ARQ response, it is not necessary to employmulti-CRC. Instead, single CRC should be employed by the system in orderto minimize the error rate by maximizing the coding length. In this way,the number of retransmissions needed can also be reduced. By contrast,for delay-intolerant but error-tolerant systems, fast ARQ response maybe required. Hence, by employing multi-CRC, unnecessary retransmissioncan be eliminated since only corrupted streams are retransmitted.

For the type III configuration, there are several ways of groupingantennas and these ways will depend on ARQ information feedback to thetransmitter. Using ARQ ACK/HACK information as a broad criterion, thequality of the antennas can be estimated. An antenna that does notrequire retransmission for its data will be deemed to be of betterquality as compared to an antenna that requires retransmission. In thiscase, the method of grouping will depend on the quality of theseantennas.

As shown in FIG. 5, the type II configuration has been chosen for thecurrent transmitted packet. For the selection of the transmission methodfor the next packet, antennas T_(x1), and T_(x2) can be grouped togethersince the probability of these two antennas requiring retransmission isnot high. On the other hand, those antennas which are more prone toretransmission will continue to employ multi-CRC technique. The aim ofemploying this type of transmission is to reduce the overheads caused byARQ feedback from all the antennas as compared to type II configuration.The type III configuration is best suited for QoS requirements that donot have tight constrains such as a low error rate and low latency.

On the other hand, if the system already employs type I or type IIItransmission as in FIG. 6, and errors occur for a particular antennagroup, the antenna configuration is selected so that the particularantenna group is divided into smaller groups of antennas, and single CRCcan be used for the divided groups of antennas, upon the nextretransmission. By dividing the antennas into smaller groups, it ispossible to reduce unnecessary retransmission and lower the latency.

In a second preferred embodiment of the present invention, the selectionof antenna configuration is performed according to ARQ feedbackinformation received at the transmitter. The transmitter will collectARQ feedback information and obtain long term ARQ statistics. Type I ischosen if the long term ARQ statistics show lower rate of retransmissionthan a predetermined value, since the increase in throughput will not besignificant if multi-CRC is employed when the rate of retransmission islow. By using type I configuration, processing at both the transmitterand receiver can be reduced.

However, if the long term ARQ feedback shows a higher rate ofretransmission than a predetermined value, type I or type III should bechosen. In this way, retransmission can be handled easily and canproceed more efficiently. Those antennas with high long-term errorperformance should have single CRC attached to a packet on each antennafor performing more efficient ARQ.

In the third preferred embodiment of the present invention, theselection of antenna configuration is performed according to channelquality feedback information received at the transmitter. In a typicalclosed-loop feedback system, the receiver usually provides thetransmitter with some particular form of channel information foradaptation purposes. For MIMO systems, the MIMO channel quality can bedetermined if channel statistics are obtained by the receiver. Fromthese statistics, the quality of each antenna can be known.

If all the antennas are known to be higher quality than a predeterminedvalue, type I configuration should be applied. That is, single CRC isadded to data to be transmitted from these antennas. The reason is thathigh quality antennas will have a lower probability of requiringretransmission and employment of type I configuration will reduce theamount of estimation processing needed.

On the other hand, if all the antennas are found to be lower qualitythan a predetermined value, type II configuration should be assignedsince the probability of requiring retransmission for such antennas ishigh. Type II configuration will improve retransmission efficiency whichwill in turn increase the overall throughput significantly.

In the case where both high and low quality antennas exist as shown inFIG. 1, type III configuration should be employed. Similar to theearlier cases, high quality antennas are grouped together and single CRCis attached to each packet to be sent from these antennas, while lowquality antennas will have CRC data attached to each packet per antenna.

In the fourth embodiment of the present invention, the selection ofantenna configuration is performed according to MCS employed by thesystem. For a system using lower MCS level than a predetermined value(for example, a system with low-level M-ary number modulation schemeQPSK and low coding rate ⅓), type I configuration is assigned. Since thedata rate for such a system will be low, the possibility ofretransmission request is low. Therefore, employing type I configurationis appropriate.

For a system using higher MCS level than a predetermined value (forexample, high-level modulation scheme 16QAM and high coding rate ¾),type II configuration should be employed. Since such a system has a highdata rate, the possibility of retransmission is high. Hence, type IIconfiguration can help the efficiency of retransmission improve.

However, if the system employs a different MCS level with respect toeach antenna as illustrated in FIG. 8, for example, if higher MCS levelthan a predetermined value is used for one of antennas and lower MCSlevel than the certain value is used for one of the other antennas,antennas transferring at a low data rate should be grouped together anda single CRC is employed for the group. On the other hand, thoseantennas transmitting at a high data rate will employ a multi-CRCconfiguration. Such a flexible type III configuration can ensureadaptability, optimization of resources of the system and optimizationof performance of the system.

In the present embodiment, the operation of receiving antennaconfiguration selection 327 of receiver completely corresponds to thatof transmitting antenna configuration selection 301 of theabove-described transmitter. For example, if type I configuration isselected by transmitting antenna configuration selection 301, type Iconfiguration is selected by receiving antenna configuration selection327. If type II configuration is selected by transmitting antennaconfiguration selection 301, type II configuration is selected byreceiving antenna configuration selection 327. If type III configurationis selected by transmitting antenna configuration selection 301, typeIII configuration is selected by receiving antenna configuration 327. Iftype III configuration is selected, details of configurations of thetransmitting side and receiving side are the same.

A result at transmitting antenna configuration antenna 301 may bereported from the transmitting side to the receiving side so as tocorrespond the result of antenna configuration selection at transmittingside to the result of antenna configuration selection at receiving side.Further, if transmitting antenna configuration selection is performed atthe receiving side, the selection result may be reported from thereceiving side to the transmitting side.

Those skilled in the art will recognize that the present inventiondiscloses a number of modifications, within the breadth and scope of thepresent inventive concepts. Although the foregoing described isconsidered the preferred embodiment of the present invention, it isunderstood that various modifications may be made therein and that theinvention may be implemented in various forms and embodiments. Thus, thebreadth and scope of the invention should not be limited to theembodiment disclosed and should be determined by reference to the claimshereinafter provided and their equivalents.

INDUSTRIAL APPLICABILITY

The wireless communication method, wireless transmitting apparatus andreceiving apparatus of the present invention are suitable for MIMOcommunication systems.

The invention claimed is:
 1. A base station, comprising: a signalgenerator configured to: select a transmission mode from a plurality oftransmission modes; in at least a case of selection of a firsttransmission mode and a case of selection of a second transmission mode:attach a first Cyclic Redundancy Check (CRC) to a first code word; andattach a second CRC to a second code word; in the case of selection ofthe first transmission mode, generate a first signal of the firsttransmission mode from the first code word with the first CRC attachedthereto and a second signal of the first transmission mode from thesecond code word with the second CRC attached thereto; and in the caseof selection of the second transmission mode, generate a first signaland a second signal of the second transmission mode from the first codeword with the first CRC attached thereto and a third signal of thesecond transmission mode from the second code word with the second CRCattached thereto; and a transmitter configured to spatially multiplexthe signals generated by the signal generator in a selected transmissionmode.
 2. The base station of claim 1, wherein the transmitter isconfigured to transmit the spatially multiplexed signals using aplurality of antennas.
 3. The base station of claim 2 wherein thetransmitter is configured to select an antenna configuration based onthe selected transmission mode.
 4. The base station of claim 1 whereinthe transmitter is configured to transmit spatially multiplexed signalsof: the first signal and the second signal of the first transmissionmode in the case of selection of the first transmission mode; and thefirst signal, the second signal and the third signal of the secondtransmission mode in the case of selection of the second transmissionmode.
 5. The base station of claim 1 wherein, in the case of selectionof the second transmission mode, the signal generator is configured togenerate a fourth signal of the second transmission mode from the secondcode word; and the transmitter is configured to transmit spatiallymultiplexed signals of the first signal, the second signal, the thirdsignal, and the fourth signal of the second transmission mode.
 6. Thebase station of claim 1 wherein, in the case of selection of the secondtransmission mode, the signal generator is configured to attach a thirdCRC to a third code word and to generate a fourth signal of the secondtransmission mode from the third code word; and the transmitter isconfigured to transmit spatially multiplexed signals of the firstsignal, the second signal, the third signal and the fourth signal of thesecond transmission mode.
 7. The base station of claim 1 wherein theplurality of transmission modes include a third transmission mode and,in a case of selection of the third transmission mode, the signalgenerator is configured to attach the first CRC to the first code wordand to generate a first signal and a second signal of the thirdtransmission mode from the first code word; and the transmitter isconfigured to transmit spatially multiplexed signals of the first signaland the second signal of the third transmission mode.
 8. The basestation of claim 7 wherein the plurality of transmission modes include afourth transmission mode and, in a case of selection of the fourthtransmission mode, the signal generator is configured to: attach thefirst CRC to the first code word; and attach the second CRC to thesecond code word; generate a first signal and a second signal of thefourth transmission mode from the first code word; and generate a thirdsignal and a fourth signal of the fourth transmission mode from thesecond code word; and the transmitter is configured to transmitspatially multiplexed signals of the first signal, the second signal,the third signal and the fourth signal of the fourth transmission mode.9. A transmitting apparatus, comprising: a signal generator configuredto select a transmission mode of a plurality of transmission modes; anda transmitter coupled to the signal generator and configured tospatially multiplex signals generated by the signal generator in aselected transmission mode, wherein in a case of selection of a firsttransmission mode of the plurality of transmission modes, the signalgenerator is configured to attach a first cyclic redundancy check (CRC)of the first transmission mode to a first code word of the firsttransmission mode; and generate a first, a second, a third and a fourthsignal of the first transmission mode from the first code word of thefirst transmission mode; and in a case of selection of a secondtransmission mode of the plurality of transmission modes, the signalgenerator is configured to: attach a first CRC of the secondtransmission mode to a first code word of the second transmission modeand attach a second CRC of the second transmission mode to a second codeword of the second transmission mode; and generate a first and a secondsignal of the second transmission mode from the first code word of thesecond transmission mode and generate a third and a fourth signal of thesecond transmission mode from the second code word of the secondtransmission mode.
 10. The transmitting apparatus of claim 9 wherein thefirst code word of the first transmission mode is a same code word asthe first code word of the second transmission mode.
 11. A transmittingapparatus, comprising: a signal generator configured to select atransmission mode of a plurality of transmission modes; and atransmitter coupled to the signal generator and configured to spatiallymultiplex signals generated by the signal generator in a selectedtransmission mode, wherein in a case of selection of a firsttransmission mode of the plurality of transmission modes, the signalgenerator is configured to: attach a first cyclic redundancy check (CRC)of the first transmission mode to a first code word of the firsttransmission mode; generate a first, a second, a third and a fourthsignal of the first transmission mode from the first code word of thefirst transmission mode; and in a case of selection of a secondtransmission mode of the plurality of transmission modes, the signalgenerator is configured to: attach a first CRC of the secondtransmission mode to a first code word of the second transmission mode,attach a second CRC of the second transmission mode to a second codeword of the second transmission mode and attach a third CRC of thesecond transmission mode to a third code word of the second transmissionmode; and generate a first and a second signal of the secondtransmission mode from the first code word of the second transmissionmode, generate a third signal of the second transmission mode from thesecond code word of the second transmission mode and generate a fourthsignal of the second transmission mode from the third code word of thesecond transmission mode.
 12. A method, comprising: selecting atransmission mode of a transmission apparatus from a plurality oftransmission modes; in at least a first and a second transmission modeof the plurality and using the transmission apparatus, attaching a firstCyclic Redundancy Check (CRC) to a first code word and a second CRC to asecond code word; in a case of selection of the first transmission modeand using the transmission apparatus, generating a first signal of thefirst transmission mode from the first code word and a second signal ofthe first transmission mode from the second code word, and transmittinga spatially multiplexed signal including the first and second signals ofthe first transmission mode; and in a case of selection of the secondtransmission mode and using the transmission apparatus, generating afirst signal and a second signal of the second transmission mode fromthe first code word and a third signal of the second transmission modefrom the second code word, and transmitting a spatially multiplexedsignal including at least the first, second and third signals of thesecond transmission mode.
 13. The method of claim 12, further comprisingselecting a configuration of a plurality of antennas based on theselected transmission mode.
 14. The method of claim 12 wherein, in thecase of selection of the second transmission mode, the method comprises:generating a fourth signal of the second transmission mode from thesecond code word; and transmitting a spatially multiplexed signalincluding the first signal, the second signal, the third signal, and thefourth signal of the second transmission mode.
 15. The method of claim12 wherein, in the case of selection of the second transmission mode,the method comprises: attaching a third CRC to a third code word andgenerating a fourth signal of the second transmission mode from thethird code word; and transmitting a spatially multiplexed signalincluding the first signal, the second signal, the third signal and thefourth signal of the second transmission mode.
 16. The method of claim12 wherein the plurality of transmission modes include a thirdtransmission mode and, in a case of selection of the third transmissionmode, the method comprises: attaching a first CRC of the thirdtransmission mode to a first code word of the third transmission mode;generating a first signal and a second signal of the third transmissionmode from the first code word of the third transmission mode; andtransmitting a spatially multiplexed signal including the first signaland the second signal of the third transmission mode.
 17. The method ofclaim 16 wherein the plurality of transmission modes include a fourthtransmission mode and, in a case of selection of the fourth transmissionmode, the method comprises: attaching a first CRC of the fourthtransmission mode to a first code word of the fourth transmission mode;attaching a second CRC of the fourth transmission mode to a second codeword of the fourth transmission mode; generating a first signal and asecond signal of the fourth transmission mode from the first code wordof the fourth transmission mode; generating a third signal and a fourthsignal of the fourth transmission mode from the second code word of thefourth transmission mode; and transmitting a spatially multiplexedsignal including the first signal, the second signal, the third signaland the fourth signal of the fourth transmission mode.
 18. The method ofclaim 17 wherein the first code word of the fourth transmission mode isa same code word as the first code word of the first and secondtransmission modes.
 19. A method, comprising: selecting a transmissionmode of a transmission apparatus from a plurality of transmission modes;in a case of selection of a first transmission mode of the plurality oftransmission modes and using the transmission apparatus, attaching afirst cyclic redundancy check (CRC) of the first transmission mode to afirst code word of the first transmission mode, generating a first, asecond, a third and a fourth signal of the first transmission mode fromthe first code word of the first transmission mode, and transmitting aspatially multiplexed signal including the first, second, third andfourth signals of the first transmission mode; and in a case ofselection of a second transmission mode of the plurality of transmissionmodes and using the transmission apparatus, attaching a first CRC of thesecond transmission mode to a first code word of the second transmissionmode, attaching a second CRC of the second transmission mode to a secondcode word of the second transmission mode, generating a first and asecond signal of the second transmission mode from the first code wordof the second transmission mode, generating a third and a fourth signalof the second transmission mode from the second code word of the secondtransmission mode, and transmitting a spatially multiplexed signalincluding at least the first, second, third and fourth signals of thesecond transmission mode.
 20. A method, comprising: selecting atransmission mode of a transmission apparatus from a plurality oftransmission modes; in a case of selection of a first transmission modeof the plurality of transmission modes and using the transmissionapparatus, attaching a first cyclic redundancy check (CRC) of the firsttransmission mode to a first code word of the first transmission mode,generating a first, a second, a third and a fourth signal of the firsttransmission mode from the first code word of the first transmissionmode, and transmitting a spatially multiplexed signal including thefirst, second, third and fourth signals of the first transmission mode;and in a case of selection of a second transmission mode of theplurality of transmission modes and using the transmission apparatus,attaching a first CRC of the second transmission mode to a first codeword of the second transmission mode, attaching a second CRC of thesecond transmission mode to a second code word of the secondtransmission mode, attaching a third CRC of the second transmission modeto a third code word of the second transmission mode, generating a firstand a second signal of the second transmission mode from the first codeword of the second transmission mode, generating a third signal of thesecond transmission mode from the second code word of the secondtransmission mode, generating a fourth signal of the second transmissionmode from the third code word of the second transmission mode, andtransmitting a spatially multiplexed signal including at least thefirst, second, third and fourth signals of the second transmission mode.21. A non-transitory memory medium whose contents configure atransmission apparatus to perform a method, the method comprising:selecting a transmission mode of the transmission apparatus from aplurality of transmission modes; in at least a first and a secondtransmission mode of the plurality, attaching a first Cyclic RedundancyCheck (CRC) to a first code word and a second CRC to a second code word;in a case of selection of the first transmission mode, generating afirst signal of the first transmission mode from the first code word anda second signal of the first transmission mode from the second codeword, and transmitting a spatially multiplexed signal including thefirst and second signals of the first transmission mode; and in a caseof selection of the second transmission mode, generating a first signaland a second signal of the second transmission mode from the first codeword and a third signal of the second transmission mode from the secondcode word, and transmitting a spatially multiplexed signal including atleast the first and second signals of the second transmission mode. 22.The non-transitory memory medium of claim 21 wherein, in the case ofselection of the second transmission mode, the method comprises:generating a fourth signal of the second transmission mode from thesecond code word; and transmitting a spatially multiplexed signalincluding the first signal, the second signal, the third signal, and thefourth signal of the second transmission mode.
 23. The non-transitorymemory medium of claim 21 wherein, in the case of selection of thesecond transmission mode, the method comprises: attaching a third CRC toa third code word and generating a fourth signal of the secondtransmission mode from the third code word; and transmitting a spatiallymultiplexed signal including the first signal, the second signal, thethird signal and the fourth signal of the second transmission mode. 24.A non-transitory memory medium whose contents configure a transmissionapparatus to perform a method, the method comprising: selecting atransmission mode of the transmission apparatus from a plurality oftransmission modes; in a case of selection of a first transmission modeof the plurality of transmission modes, attaching a first cyclicredundancy check (CRC) of the first transmission mode to a first codeword of the first transmission mode, generating a first, a second, athird and a fourth signal of the first transmission mode from the firstcode word of the first transmission mode, and transmitting a spatiallymultiplexed signal including the first, second, third and fourth signalsof the first transmission mode; and in a case of selection of a secondtransmission mode of the plurality of transmission modes, attaching afirst CRC of the second transmission mode to a first code word of thesecond transmission mode, attaching a second CRC of the secondtransmission mode to a second code word of the second transmission mode,generating a first and a second signal of the second transmission modefrom the first code word of the second transmission mode, generating athird and a fourth signal of the second transmission mode from thesecond code word of the second transmission mode, and transmitting aspatially multiplexed signal including at least the first, second, thirdand fourth signals of the second transmission mode.
 25. A non-transitorymemory medium whose contents configure a transmission apparatus toperform a method, the method comprising: selecting a transmission modeof the transmission apparatus from a plurality of transmission modes; ina case of selection of a first transmission mode of the plurality oftransmission modes, attaching a first cyclic redundancy check (CRC) ofthe first transmission mode to a first code word of the firsttransmission mode, generating a first, a second, a third and a fourthsignal of the first transmission mode from the first code word of thefirst transmission mode, and transmitting a spatially multiplexed signalincluding the first, second, third and fourth signals of the firsttransmission mode; and in a case of selection of a second transmissionmode of the plurality of transmission modes, attaching a first CRC ofthe second transmission mode to a first code word of the secondtransmission mode, attaching a second CRC of the second transmissionmode to a second code word of the second transmission mode, attaching athird CRC of the second transmission mode to a third code word of thesecond transmission mode, generating a first and a second signal of thesecond transmission mode from the first code word of the secondtransmission mode, generating a third signal of the second transmissionmode from the second code word of the second transmission mode,generating a fourth signal of the second transmission mode from thethird code word of the second transmission mode, and transmitting aspatially multiplexed signal including at least the first, second, thirdand fourth signals of the second transmission mode.